滇黔桂岩溶区河漫滩土壤重金属含量、来源及潜在生态风险

利用全国地球化学基准计划在滇黔桂岩溶区35个点位采集的70件河漫滩表、深层土壤样品，分析了As、Cd、Cr、Cu、Hg、Ni、Pb和Zn 8种重金属元素含量特征，探究了重金属来源、污染状况及潜在生态风险.结果表明，8种重金属元素含量大部分均高于全国土壤背景值，在滇东南地区含量最高，桂西北地区最低.表层土壤Cd、Hg明显富集，As、Cr、Cu、Ni与深层土壤含量相当；As、Cd、Hg、Pb、Zn在农田、菜地中明显高于深层土壤，Cr、Cu和Ni在各类土地中与深层土壤相当.因子分析结果显示，表层土壤中Cd、Cr、Cu、Ni受地质背景控制，As、Pb、Zn既与地质背景有关，也受人为活动影响，Hg受人为活动影响较严重；深层土壤中Cd、Cr、Cu、Ni、Cr、Zn继承了区域母岩特征，As、Hg和Pb受地质背景和人为活动双重影响.地累积指数法和富集因子法污染评价结果表明，研究区河漫滩表层土壤中Cd、Hg污染较重，As、Cr、Cu、Ni、Pb、Zn大部分为轻度污染或无污染.各重金属潜在生态风险指数高低顺序依次为Hg > Cd > As > Cu > Ni > Pb > Cr > Zn，Cd和Hg的生态风险指数之和占综合指数的82.43%，生态风险最高；滇东南地区重金属潜在风险综合指数最高，具重度生态风险.

Distribution,sources and potential ecological risk of heavy metals in the floodplain soils of the karst area of Yunnan,Guizhou, Guangxi

Seventy floodplain soil samples were collected by the CGB sampling team at 35locations in the karst area of Yunnan, Guizhou, Guangxi to study the distribution, sources, the pollution degree and ecological risk of 8heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) by factor analysis, geo-accumulation index (I_geo), enrichment factor (EF) and the Hakanson's potential ecological risk index (E_rⁱ and RI) methods. Results showed that the concentrations of all elements were almost higher than their soil background values of China. Cd and Hg were significantly enriched in the top soils, while As, Cr, Cu, Ni were similar in top and deep soils. The high values of heavy metals were concentrated in southeast of Yunnan, while the low values were concerted in northwest of Guangxi. The contents of As, Cd, Hg, Pb and Zn in top soil from farmland and vegetable land were significantly higher than those in deep soil, while the Cr, Cu and Ni were comparable to those in deep soil from all land-uses. The Factor analysis results indicated that Cd, Cr, Cu and Ni in the top soils were mainly affected by geological background, As, Pb and Zn were not only related to the natural conditions, but also affected by human activities, Hg were affected by anthropogenic contamination; all heavy metals were inherited the characteristics of regional parent rocks in deep soil, while As, Hg and Pb were also affected by human activities. The results of I_geos and EFs showed that Cd and Hg were seriously polluted in the top soils, As, Cr, Cu, Ni, Pb and Zn were mainly light polluted or non-polluted. The ecological risk calculated by ecological risk indexes (E_rⁱ) were ordered by Hg > Cd > As > Cu > Ni > Pb > Cr > Zn. The sum E_rⁱ of Cd and Hg accounted for 82.43% of the comprehensive indexes of potential ecological risks (RI), indicated that the top soil of floodplain occured high potential ecological risk of Cd and Hg. Moreover, the southeast of Yunnan had the highest RI of heavy metals, and had the severe ecological risk in the study area.